臺灣⾼海拔針葉林之植群多樣性

Vegetation Diversity of High-mountain Coniferous Forests of Taiwan

林政道(Cheng-Tao Lin)

指導教授 ： 邱祈榮

國立臺灣大學/生物資源暨農學院/森林環境暨資源學研究所/博士(2014年)

https://doi.org/10.6342/NTU.2014.01863

摘要

主要分布在北半球⾼緯度的針葉林對於植群⽣態學及巨觀⽣態學⽽⾔是很重要的研究議題。從植物社會學的⾓度來看，和越橘－雲杉群級(Vaccinio-Piceetea) 相關的優勢種多是為冷杉屬、雲杉屬、鐵杉屬及落葉松屬的物種。⽽在臺灣帶狀分布的針葉林主要分布在⾼海拔的⼭區，其主要的優勢種為臺灣冷杉、臺灣鐵杉、臺灣雲杉、⽟⼭圓柏等。根據蘇鴻傑教授(Su, 1984b) 的植群分類系統，這些⾼海拔植群屬於「亞⾼⼭針葉林」及「上部⼭地針葉林」。此外普遍分布於針葉林林下或形成開放草原的⼀種矮箭⽵—⽟⼭箭⽵是在⾼海拔⼭地帶特殊的景觀。這些矮箭⽵的出現通常被推論為⽕災⼲擾後⽽形成，並可能影響到針葉林物種的更新，⽽這些分布於林下的矮箭⽵亦是區別不同植群型的重要特徵。本論⽂使⽤國家植群多樣性調查及製圖計畫資料庫(簡稱臺灣植群資料庫) 中的物種組成資料，並使⽤Braun-Blanquet 分析法來分類臺灣⾼海拔的針葉林。環境因⼦中的坡度、坡相、全天光空域等是使⽤GIS 從數值地形圖計算得來，其他的⼟壤含⽯率、地形等因⼦則由野外估測取得。氣候因⼦則是根據臺灣植群資料庫中之樣區點位，從WorldClim 資料庫中抽取其最⼤、最⼩及平均溫度和累積⾬量等數值，並計算出不同的⽣物氣候因⼦來分析。在資料探索階段中，植群分類是使⽤叢集分析，並根據分析結果建⽴植相分類的基本單位，如群團及群叢等。在本研究中，共分類並定義出九個群叢，分別屬於兩個群團。第⼀個群團是⽟⼭圓柏群團，包含了三個群叢：單花牻⽜兒苗－⽟⼭圓柏群叢、臺灣烏頭－⽟⼭圓柏群叢及⽟⼭圓柏－臺灣冷杉群叢。本群團特徵為冠層為優勢之⽟⼭圓柏所組成及地被為亞⾼⼭的草原物種所組成，並零星分布於⾼海拔⼭區的灌叢及森林。第⼆個群團則是臺灣冷杉－臺灣鐵杉群團，其包含了六個群叢：⽟⼭箭⽵－臺灣冷杉群叢、臺灣鐵杉－臺灣冷杉群叢、⽟⼭箭⽵－臺灣鐵杉群叢、臺灣華⼭松－臺灣鐵杉群叢、⽟⼭杜鵑－臺灣鐵杉群叢及海螺菊－臺灣雲杉群叢。本群團的植相特徵包含了亞⾼⼭區域以臺灣冷杉及臺灣鐵杉及耐蔭性草本物種所組成的植群。另外⽐對區域性植群型後，臺灣⾼海拔針葉林的植相組成並不屬於越橘－雲杉群綱，⽽是和中國西南部⼭地針葉林相關，並可能成為⼀個新的亞熱帶⾼海拔針葉林群綱。此外，為了要釐清臺灣⾼海拔冷杉林林下⽟⼭箭⽵與臺灣冷杉的關係，在本研究中使⽤臺灣冷杉林物種組成、⾮⽣物性因⼦、⽟⼭箭⽵的相對頻度並透過⾮計量多維度尺度分析及結構⽅程模式來建⽴其因果關係之確認。結果顯⽰影響臺灣冷杉物種組成主要是受到溫量指數及冬季降⽔的影響，⽽⽟⼭箭⽵相對頻度則對冷杉林地被物種的組成具有強烈的影響。更進⼀步檢視影響⽟⼭箭⽵相對頻度的因⼦中，⼟壤含⽯率對於其頻度具有⾼度的負⾯影響效應，但冬季降⽔則具有正⾯的影響。因此可以推論⽟⼭箭⽵的頻度則是主要受到⼟壤厚度及棲地岩⽯地⽐例影響。

關鍵字

植物社會學 ； 臺灣冷杉 ； 臺灣鐵杉 ； 植群分類 ； ⽟⼭箭⽵ ； 群團分析

並列摘要

The coniferous forests widely distributed in the high latitude of northern hemisphere are important on vegetation ecology and macroecology. In the view of phytosociology, the boreal and oroboreal coniferous forests dominated by several species of Abies, Picea, Tsuga, Larix, etc. are related to phytosociological class Vaccinio-Piceetea. The zonal coniferous forests in Taiwan are mainly distributed in the high-mountain regions, and the dominant species are Abies kawakamii, Tsuga chinensis var. formosana, Picea morrisonicola and Juniperus squamata. In the previous classification scheme, they were classified as subalpine coniferous forests and upper-montane coniferous forests according to Su’s classification scheme. However, in the subalpine and mountainous belt, the prevalent dwarf bamboo, such as Sasa sp., Yushania sp. usually occurs in the understory or forms open grasslands at disturbed regions. The occurrence of these dwarf bamboo was usually proposed to postfire and would be related to the regeneration of coniferous species. The existence of these dwarf bamboo would be an important character to identify different vegetation types. In this dissertation, the species data were extracted from the database of National Vegetation Diversity Inventory and Mapping Project and used to classify the high-mountain coniferous forests based on Braun-Blanquet approach. The environmental variables including aspect, site openness and slope related to syntaxa were calculated from the GIS database based on digital elevational map, while soil rockiness, topography were estimated in the field. The climatic factors including maximum, minimum and mean temperature, and precipitation were obtained from WorldClim database and calculated bioclimatic factors, such as warmth index, precipitation of summer, etc. for analysis. In the exploratory analysis stage, cluster analyses (i.e. principal component analysis, non-metric multidimensional scaling) were used to classify vegetation plots and established phytosociological units, such as alliances and associations. Nine associations belonging to two alliances were defined in this study.
The first alliance Juniperion squamatae including three associations: Geranio hayatanum-Juniperetum squamatae, Aconito fukutomei-Juniperetum squamatae and Junipero squamatae-Abietetum kawakamii. It represents woodlands and forests scattered in the subalpine region, in which Juniperus squamata dominates the canopy and subalpine meadow species occur in the understorey. The second alliance Abieti kawakamii-Tsugion formosanae includes six associations: Yushanio niitakayamensis-Abietetum kawakamii, Tsugo formosanae-Abietetum kawakamii, Yushanio niitakayamensis-Tsugetum formosanae, Pino mastersianae-Tsugetum formosanae, Rhododendro pseudochrysanthum-Tsugetum formosanae and Ellisiophyllo pinnati-Piceetum morrisonicolae. It is represented by forests composed of dominated Abies kawakamii and Tsuga chinensis var. formosana with shade-adapted herb species in the upper montane regions. Comparing the floristic compostion in the class level, the high-mountain coniferous forests of Taiwan does not belong to Vaccinio-Piceetea, and they would be a novel phytosociological class in the subtropical high-mountain areas. In order to clarify the relationship between Yushania niitakayamensis in the understory of Abies kawakamii forest in Taiwan, the species composition, abiotic factors and relative frequency of Yushania niitakayamensis was examined throughout the assessment
by non-metric multidimentional scaling and structural equation modeling. The result suggest that the warmth index and precipitation of winter are strong indirect drivers to the species composition of Abies kawakamii forest in Taiwan, while the relative frequency of Yushania niitakayamensis have strong influence on the understory species composition. Furthermore, the soil rockiness determined the relative frequency of Yushania niitakayamensis and had strong negative effect, but the precipitation of winter contributed it as a positive direct factor. However, the prevalence of Yushania niitakayamensis would attribute to high ratio of habitat rockiness and thick soil.

並列關鍵字

phytosociology ； Abies kawakamii ； Tsuga chinensis var. formosana ； vegetation classification ； Yushania niitakayamensis ； cluster analysis ； structural equation modeling

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